Field of the Invention
The present invention relates to a base, a liquid discharge head, a printing apparatus, and a method for determining an ink discharge status and, particularly, to a printing apparatus which uses a liquid discharge head including heating elements (heaters) for discharging liquid such as ink, and a method for determining a liquid discharge status.
Description of the Related Art
One of inkjet printing methods for discharging ink droplets from nozzles and adhering them to a print medium such as paper or a plastic film uses a liquid discharge head including heaters configured to generate heat energy for discharging ink. For the liquid discharge head according to this method, an electrothermal transducer which generates heat in accordance with energization, a driving circuit, and the like can be formed by a process similar to a semiconductor manufacturing process. Therefore, high-density integration of nozzles is easy, and high-resolution printing can be implemented.
In this liquid discharge head, ink discharge failure may occur in all or some nozzles of the liquid discharge head due to nozzle clogging caused by a foreign substance, ink of high viscosity, or the like, a bubble entering an ink supply channel or nozzle, a change in wettability of a nozzle surface, or the like. To avoid degradation of the image quality in a case where such discharge failure occurs, it is desirable to quickly execute a recovery operation of recovering the ink discharge status, and a complementary operation using another nozzle or the like. However, to quickly perform these operations, it is very important to determine the ink discharge status and occurrence of discharge failure accurately and timely.
Hence, there have conventionally been proposed various methods for determining the ink discharge status and apparatuses to which these methods are applied.
Japanese Patent Laid-Open No. 2007-290361 discloses a method for comparing, with a predetermined threshold, the highest temperature in ink discharge, which has been detected by a temperature detection element provided immediately below a heater, in order to detect the ink discharge status. When ink is normally discharged, heat is transferred from the heater together with discharged ink droplets. To the contrary, in an ink discharge failure, no ink is discharged, and thus heat is accumulated in an interlayer insulation film to raise the highest temperature. In accordance with a difference in highest temperature, it is possible to detect the ink discharge status.
To detect a discharge failure, Japanese Patent Laid-Open No. 2008-000914 discloses a method for detecting a decrease in temperature in normal discharge. In normal discharge, part of a discharged ink droplet comes into contact with an anti-cavitation film, and the temperature of a temperature detection element abruptly lowers. To the contrary, in ink discharge failure, no ink droplet comes into contact with the anti-cavitation film, and the temperature of the temperature detection element gradually lowers. Therefore, in accordance with a difference in temperature change, it is possible to detect the discharge status.
In the discharge status determination method disclosed in Japanese Patent Laid-Open No. 2007-290361, however, since the reached highest temperature changes depending on the temperature of the liquid discharge head, applied energy, a difference in resistance value of the temperature detection element, or the like, a determination threshold according to each condition is required.
In the arrangement disclosed in Japanese Patent Laid-Open No. 2008-000914, to detect an abrupt decrease in temperature, the peak of the temperature change is emphasized by executing a plurality of calculation processes such as differential processing for the detected temperature. Thus, it takes time to perform processing up to determination. Furthermore, the circuit scale becomes large due to the calculation processing.